Conventional three-wheeled vehicles have two wheels in back and one in front, or alternatively, two wheels in front and one in back. Tricycles with two wheels in back are more traditional and utilize the single wheel in front for steering. Tricycles with two wheels in front often employ the single rear wheel for steering; however, others utilize both the front wheels for steering.
The conventional rigid frame structure of most tricycles tends to cause one of the wheels of the pair of wheels in the direction of a turn to lift off the ground. At high speeds, such tricycles have been known to tip over.
Many elaborate and complicated tricycles have been developed in an effort to avoid this tipping effect. A search by the applicant has revealed the following patents.
U.S. Pat. Nos. 4,740,004; 4,634,137; and 3,561,778 disclose tricycles with two front wheels utilizing parallel bar linkage to allow the frame and front wheels to bank upon turning.
U.S. Pat. Nos. 4,132,435; 3,958,814; 3,836,177; and Design U.S. Pat. No. 290,451 disclose tricycles with two front wheels utilizing transverse front axles and means to allow the frame to tilt relative to the front axle.
U.S. Pat. No. 4,360,224 discloses another tricycle having two front wheels. These wheels are mounted on a suspension assembly which is mounted on a longitudinally extending shaft connected to the frame.
U.S. Pat. No. 3,937,486 discloses a tricycle having two rear wheels wherein the frame is rotatable upon a solid rear axle or wherein a pair of independent rotatably mounted axles prevent the rear wheels to be directed in the direction of turn.
U.S. Pat. No. 3,799,565 discloses a recreation vehicle which in one embodiment is a tricycle having a linkage assembly that allows a pair of rear wheels to be tilted as the tricycle is turned.
Conventional tricycles typically utilize the single wheel, be it in front or rear, as the driven wheel. When the tricycle is driven by the single rear wheel, the forward propelling forces are not in the direction of movement of the tricycle during turning. Although this is overcome in the single front wheel driven tricycles, therein the driving apparatus is mounted on the front end of the tricycle which adversely affects steering.